Seek Statement

Description

Sets the position for the next read/write operation within a file opened using the Open statement.

Syntax

Seek [#]filenumber, position

The Seek statement syntax has these parts:

Part	Description

filenumber	Required. Any valid file number.
position	Required. Number in the range 1 – 2,147,483,647, inclusive, that indicates where the next read/write operation should occur.

Remarks

Record numbers specified in Get and Put statements override file positioning performed by Seek.

Performing a file-write operation after a Seek operation beyond the end of a file extends the file. If you attempt a Seek operation to a negative or zero position, an error occurs.

See Also

Get statement, Loc function, Open statement, Put statement, Seek function.

Example

This example uses the Seek statement to set the position for the next read or write within a file. This example assumes TESTFILE is a file containing records of the user-defined type Record.

Type Record                                    ' Define user-defined type.
    ID As Integer
    Name As String * 20
End Type

For files opened in Random mode, Seek sets the next record.

Dim MyRecord As Record, MaxSize, RecordNumber    ' Declare variables.
' Open file in random-file mode.
Open "TESTFILE" For Random As #1 Len = Len(MyRecord)
MaxSize = LOF(1) \ Len(MyRecord)        ' Get number of records in file.
' The loop reads all records starting from the last.
For RecordNumber = MaxSize To 1 Step - 1
    Seek #1, RecordNumber                    ' Set position.
    Get #1, , MyRecord                        ' Read record.
Next RecordNumber
Close #1                                        ' Close file.

For files opened in modes other than Random mode, Seek sets the byte position at which the next operation takes place. Assume TESTFILE is a file containing a few lines of text.

Dim MaxSize, NextChar, MyChar
Open "TESTFILE" For Input As #1        ' Open file for input.
MaxSize = LOF(1)                            ' Get size of file in bytes.
' The loop reads all characters starting from the last.
For NextChar = MaxSize To 1 Step -1
    Seek #1, NextChar                        ' Set position.
    MyChar = Input(1, #1)                    ' Read character.
Next NextChar
Close #1                                        ' Close file.